The invention relates generally to a unipolar diode and more particularly to a unipolar diode with a low turn-on voltage.
Diodes are a fundamental electronic building block. Their ability to restrict current flow to substantially one direction is a critical property relied upon in virtually every electronic circuit manufactured, from the smallest power supply to the largest industrial process controller.
Mixer and detector circuits use non-linearity in the diode turn-on characteristics to up-convert or down-convert RF signals to either intermediate signals or baseband. To operate, the voltage on the diode must be in the range of its turn-on voltage. This can be accomplished either by biasing the diode with a DC power supply or by providing sufficient radio frequency (RF) or local oscillator (LO) power to self-bias the diode. Introducing bias circuitry to bias the diode increases noise, increases circuit size, increases circuit DC power consumption, increases the conversion loss of the circuit, and decreases the frequency performance of the circuit, so self-biasing is preferred. In order to minimize the required RF or LO power to self-bias the diode, minimizing diode turn-on voltage is desirable.
The capacitance associated with the charge variation in a diode's depletion layer is the junction capacitance. It is generally desirable to minimize a diode's junction capacitance. The barrier height of a diode refers to the potential barrier that must be overcome to turn on the diode.